1. Field of the Invention
The present invention relates to a thin film magnetic head which can be employed for information processing devices such as personal computers or workstations, and which has a magnetoresistive element portion that moves over and relative to a magnetic writing or recording medium (hereinafter referred to as a recording medium), such as a hard or floppy disk, to read stored information.
2. Description of Related Art
Thin film magnetic heads have been conventionally employed in effecting high density recording of information onto the recording medium. One example of such thin film magnetic heads is described in Japanese Patent Laying-open No. Hei 6-223331 (1994). FIG. 7 is a schematic cross-sectional view of such a prior art magnetic head.
As shown in FIG. 7, the prior art thin film magnetic head has a substrate 1 on which an insulative layer 20 formed of diamond-like carbon (hereinafter referred to as DLC), a shielding layer 3, an insulative layer 21 formed of DLC, a magnetoresistive element portion (hereinafter referred to as an MR element layer 5), lead layers 6-A and 6-B, an insulative layer 22 formed of DLC, and a shielding layer 8 are stacked in such a consecutive order.
FIG. 8 is a partly enlarged view of the MR element layer 5 and lead layers 6-A and 6-B in FIG. 7.
Referring now to FIGS. 7 and 8, the lead layers 6-A and 6-B are coupled to opposite ends of the MR element layer 5. The MR element layer 5 has a nonmagnetic interlayer 11 sandwiched between a magnetoresistive layer 12 and a soft magnetic layer 10 which is closest of the three to the substrate 1. The soft magnetic layer 10 is a film for applying a bias electric field to the magnetoresistive layer 12. The nonmagnetic interlayer 11 is a film for magnetically isolating the soft magnetic layer 10 from the magnetoresistive layer 12 which is a film for converting magnetic flux changes to signals.
Each of the lead layers 6-A and 6-B has an antiferromagnetic bias layer 13 on which an adherence enhancing layer 14 and a conductive lead layer 15 are consecutively stacked. The lead layers 6-A and 6-B define an operational region 6-C therebetween.
When desired to read information stored in the recording medium using the above-described thin film magnetic head, a rated current is applied to the lead layer 6-A to allow the rated current to flow therefrom through the MR element layer 5 to the lead layer 6-B. The current flowing into the MR element layer 5 produces an electric field perpendicular to a direction of the current flow, inducing magnetic fields in the magnetoresistive layer 12 as well as the soft magnetic layer 10, so that the magnetoresistive layer 12 is biased in the direction of the current flow through a coupling effect.
When subjected to an external magnetic field while in such a biased state, the magnetoresistive layer 12 changes in its resistance with varying magnetic field. The output can be obtained by processing the resistance changes as signals.
However, DLC layers are generally high in internal stress, particularly in compressive stress. Due to the action of this compressive stress, a tensile force acts on a body adhered to the DLC.
In the above-described thin film magnetic head, the lead layers 6-A and 6-B, as well as the MR element layer 5, are sandwiched between the insulative layers 21 and 22. Accordingly, the compressive forces generated in the insulative layers 21 and 22 are likely to act to deform the MR element layer 5, leading to failure of obtaining desired electrical characteristics and, as a consequence, loss of reliability.
Furthermore, forming the insulative layers having a high compressive stress directly on the shielding layers, as described above, is very likely to cause upper layers including the insulative layers to be delaminated from the substrate when subjected to the action of compressive forces in the insulative layers.